This invention pertains to hoppers and feeders, and particularly to hoppers from which envelopes are extracted for use in a postal preparatory processing machine, such as an insertion machine or the like.
Traditional envelope hoppers have trouble handling both large envelopes (such as envelopes measuring on the order of 9.0 inches.times.12.0 inches or larger) and short envelopes (such as envelopes measuring on the order of 9.5 inches.times.4.0 inches or smaller). In one such prior art envelope hopper four vertical walls of a hopper are constructed to surround a stack of horizontally-oriented large envelopes. The bottom-most envelope of the stack rests on a horizontal breaker plate which extends from a back vertical wall toward but short of a front vertical wall. In this regard, the breaker plate terminates at a breaker plate front edge which lacks a few inches of reaching the front vertical wall. One or more suction mechanisms, positioned just below the plane of the breaker plate but between the breaker plate front edge and the front vertical wall, (function to reflect downwardly at least a portion of the bottom most envelope which is lying on and overhanging the breaker plate of the hopper) so that the bottom-most envelope can be engaged by appropriate gripper means situated proximate the front of the hopper; be extracted from the hopper; and, be transported away from the hopper for downstream postal preparatory processing.
In the hopper described above small envelopes are loaded with their major dimension parallel to the front vertical wall, and hence parallel to the breaker plate front edge. Since the breaker plate front edge is separated from the front vertical wall by a distance which is on the order of one-half the minor dimension of the small envelopes, a considerable amount of each small envelope overhangs the breaker plate front edge relative to the entire small envelope. When a stack of small envelopes are so loaded into such a hopper, the small envelopes tend not to lie horizontally, but instead tend to tip over the breaker plate front edge so that the envelopes in the stack are inclined at an acute angle to the breaker plate. The inclined plurality of envelopes cause a jam when the gripper means attempts to extract the bottom-most envelope.
Since the aforedescribed hopper has trouble in handling small envelopes, various prior art hoppers have been specially constructed to handle small envelopes. Unfortunately, these special hoppers do not handle large envelopes with equal facility. One type of prior art special hopper comprises two sets of vertical rods, each set positioned in parallel relationship along the major dimension of a space corresponding to a small envelope. Each set of rods has mounted thereto a horizontal ledge which faces and is coplanar with the ledge of the other set of rods. The major dimensional edges of a bottom-most envelope rest upon these ledges. Other envelopes are stacked upon the bottom-most envelope and between the vertical rods. A mechanism is situated below the plane of the ledges. When suction is applied, the formerly horizontally-oriented bottom-most envelope is bowed downwardly and eventually entirely sucked onto a planar surface parallel to but beneath the ledges. A reciprocating pusher mechanism (travelling from behind the hopper in a direction parallel to the major dimension of the small envelope) moves toward the envelope (which has been sucked beneath the stack); contacts the envelope; and, pushes the envelope into the jaws of awaiting gripper means in front of the hopper. This type of prior art envelope hopper works well for small envelopes which have sufficient beam strength across their minor dimension. If, however, the two sets of vertical rods defining the envelope stack become sufficiently displaced from one another in order to accommodate larger envelopes, the large envelopes sag due to the lack of beam strength characterizing such envelopes. A stack of sagging large envelopes precludes the pusher mechanism and gripper from functioning effectively.
Yet another type of prior art hopper specially adapted to handle small envelopes comprises a shuttle feed mechanism. The shuttle feed mechanism includes an essentially rectangular horizontal plate which reciprocates in its horizontal plane in a direction from the back of the hopper toward the front of the hopper. One of the concerns on the leading edge of the shuttle plate is truncated to define a triangular space. When the shuttle plate is in a position nearest the back of the hopper, a stationary first suction mechanism lies below the triangular space. The stationary first suction mechanism serves to deflect downwardly a corresponding corner of the bottom-most small envelope. A second suction mechanism situated on the other corner of the leading edge of the shuttle place also engages the bottom-most envelope and travels with the shuttle plate as the plate and bottom-most envelope held by the shuttle plate are advanced to the front of the hopper by the motion of the reciprocating shuttle plate. At the front of the hopper the appropriate gripper means engages the advanced envelope in like manner as described above and transports the advanced envelope away from the hopper. While the shuttle plate of this second type of envelope hopper functions well to extract small envelopes, the shuttle plate does not have enough suction to both attract a large envelope and cause the large envelope to reciprocate therewith in the direction of the gripper means.
In view of the foregoing, an object of this invention is the provision of an envelope hopper which handles both large and small envelopes with equal facility.